ROSAT observations of 3C radio-loud sources

The 3CRR sample of radio galaxies and quasars has been cross-correlated with the ROSAT/PSPC All-Sky Survey. About 25% of the objects have been detected in the 0.2-2.4 keV range, the large majority being powerful radio and X-ray emitters with a range of X-ray luminosities between 10"4"4 and 10"4"6 erg/sec. The 0.2-2.4 keV spectrum of the radio-loud sources is found to be well characterised by a single power-law continuum absorbed by typical Galactic H column densities. The range of power-law spectral indices (-1.5<#alpha#<-0.2) clusters around #alpha##propor to#-1., and is in general steeper than those measured for radio-loud sources at energies above 2 keV. Thus, the presence of a soft X-ray excess component in radio-loud sources is found to be a common feature in the spectrum of these objects. However, factors not yet known inhibit its presence in some sources. This soft excess appears to be of the same nature as that seen in their radioquiet counterparts, the only difference being a slight steepening of the spectrum in the latter. Emphasis is put of the close similarity between the radio and the high energy (typically 2-10 keV) spectral indices for the lobe-dominated sources in the sample. Though in only five of the sources an individual cross-checking could be done, there is an overall agreement between the radio and the hard X-ray spectra slopes in lobe-dominated sources which may be suggesting the same spectral distribution of particles energy in the core and lobes of radio sources. (orig.)Available from TIB Hannover: RN 9303(359) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman